Cognitive processing load as a determinant of stuttering: Summary of a research programme

Abstract

The present paper integrates the results of experimental studies in which cognitive differences between stuttering and nonstuttering adults were investigated. In a monitoring experiment it was found that persons who stutter encode semantic information more slowly than nonstuttering persons. In dual-task experiments the two groups were compared in overt word-repetition and sentence-production experiments. The results of the two word-repetition experiments indicate that the speech of stuttering persons is sensitive to interference from concurrent attention-demanding cognitive processing-particularly when phonological coding is involved. In two sentence-generation and -production experiments it was found that under dual-task conditions stuttering persons produced sentences containing a smaller number of content units whereas persons who do not stutter did not show a significant single- vs. dual-task contrast. These results suggest that sentence generation and production required greater sustained attentional processing in stuttering than in nonstuttering persons and that persons who stutter reduce the amount of "conceptual work" in order to keep their stuttering rates low. Data from an fMRI-study indicate that in persons who stutter the neural systems activated during sentence generation and production overlap to a greater extent than those of persons who do not stutter. It is suggested that in persons who stutter neural subsystems involved in speech planning are "modularized" to a lesser extent than in persons who do not stutter.

Influences of rate, length, and complexity on speech disfluency in a single-speech sample in preschool children who stutter

“…A model relating to task demands that may partially explain the data presented here has been proposed by Bosshardt (2006). In a series of investigations, Bosshardt and colleagues have found that adults who stutter produce either shorter and less grammatically complex utterances or more disfluency under dual task conditions, in which attention is divided (e.g., Bosshardt, 2002;Bosshardt, Ballmer, & de Nil, 2002).…”

“…These investigations point to differences in cognitive processing in people who stutter and normally fluent speakers. Bosshardt (2006) has suggested that people who stutter are vulnerable to increased processing loads, perhaps due to an overlap in functioning in speech-motor and speech planning areas of the brain. Looking at the data from the current study from the viewpoint of Bosshardt's model, it could be said that the longer utterances in section B required more cognitive resources to generate than the shorter utterances in Section A, with more disfluencies resulting.…”

“…Planning time required for the construction of longer, more complex utterances might have a negative effect on fluency. Adults who stutter have been found to produce shorter utterances and more disfluency than those with normal fluency under dual-task processing conditions (Bosshardt, 2006). Bosshardt (2006) has proposed that vulnerability to increased cognitive processing loads precipitates stuttering.…”

“…Increased length and complexity have been viewed as an increase in processing demands, and people who stutter are more vulnerable to such increases (Bosshardt, 2006). A fast speech rate could be another processing demand that results in increased disfluency.…”

Effects of Length, Complexity, and Grammatical Correctness on Stuttering in Spanish-Speaking Preschool Children

“…The impact of increased length and syntactic complexity on the fluency of young children lends support for psycholinguistic theories of stuttering, which suggest that syntactic, lexical, phonological, or suprasegmental aspects of speech production may play a role in the expression of stuttering (Bernstein Ratner, 1997). In addition, in studies of adults who stutter, it has been proposed that increased processing demands, such as those associated with increased length and /or linguistic complexity, may lead to fluency disruptions (Bosshardt, 2006). Others have explored the relationship between linguistic encoding difficulties and related motor instabilities, with outcomes suggesting that the motoric stability of persons who stutter may be uniquely vulnerable to increases in linguistic complexity .…”